So, the current ones seem a bit too loud and doesn't really fit the atmosphere. Your choice of audio should depend on how you want the player to feel when playing the game this is especially required if you're considering to add music for the environment. For the car sounds, I recommend going for a more pleasant sound. Also, consider adding particle systems when vehicles collide with each other giving an impression the car has hit something. For the map, if you're going for a city, it has to be lively, cuz if you have a huge city but little to no detail in terms of interactive elements, it can get quite boring for the player. I recommend maybe adding destructive elements like road signs, benches and lights for the player to knock down.
